1. Field of the Invention
The invention relates to a method for producing fine grained, sintering active nitride and/or carbonitride powder of titanium as well as, optionally, of other metals of the IVA, VA and VIA group of the periodic table of elements.
Cutting materials on the basis of tungsten carbide with or without additives of carbides of the elements of the IVA, VA and VIA group of the periodic system have long been known as hard metals and have found a wide field of application.
In the last few years a new group of cutting materials has been developed which is known under the name of "Cermets". Such metal-ceramic materials essentially consist of a metallic binder phase and a ceramic hard solid component such as nitride, carbide or carbonitride of titanium, optionally with additives of carbides, nitrides or carbonitrides of further elements of the IVA, VA and VIA group of the periodic system. The metallic binder phase is usually nickel. The optimization of the properties for the various fields of application is to be achieved by altering the proportion of binder phase, the size of the hard solid particles, the ratio between carbon and nitrogen, and by addition of other hard solids of the above-mentioned groups of the periodic system. Cermet cutting materials are generally characterized by a tuned relationship between abrasive resistance and tenacity. Compared with common hard metals, said cermets provide improved abrasive properties and a lower tendency of diffusion. Said cermets are particularly suitable for working ductile materials at high cutting speeds with low cutting depths in order to achieve the highest surface qualities in the shortest possible time. The hard solid components contained in the cermets, in particular the nitride and/or carbonitride of titanium, should be as fine-grained and as pure as possible. The content in oxygen is a special criterion as it influences the wetting behaviour with regard to the binder phase. In many cases it might be desirable to homogenously build additives of further carbides, nitrides or carbonitrides of the elements of the IVA, VA and VIA group of the periodic system into the titanium carbonitride mixed crystal.
2. Description of Prior Art
Literature provides a number of methods for manufacturing titanium nitride or titanium carbonitride with or without further additives.
Presently, titanium carbonitride with optional further additives is mainly manufactured by reaction annealing of a mixture consisting of titanium carbide and, optionally, additives of further carbides and titanium nitride, said annealing taking place under nitrogen at temperatures of around 1500.degree. C. A further possibility for the specific production of nitrides consists of transforming the respective metal powder by means of nitrogen, whereby carbon may also be added. In accordance with the reaction of titanium oxide with carbon and nitrogen, which was examined by E. Friederich and L. Sittig in 1925, one also receives titanium nitride with a more or less high content of carbon. When a reaction temperature of approx. 1250.degree. C. is applied, one gains a bluish product which points out to a high content of oxygen. To achieve a low content of oxygen in the product, it is necessary, as is well known, to apply temperatures of around 2000.degree. C. The low-oxygen nitride or carbonitride comprises grain sizes which require the product to be finely comminuted in ball mills, triturators etc. at high costs. During the process, undesirable impurities enter the material to be ground. In many cases it is near impossible to reach the grain size of &lt;2 .mu.m which is used in the application. By transforming titanium tetrachloride with nitrogen and hydrogen or ammonia one receives extremely fine-grained titanium nitride. The high costs and the product's unstableness in the air as a consequence of the low grain size are the disadvantages of this method.